Trenton, N.J. ? Pediatricians rushed to stock up on a crucial baby shot Thursday, a day after one of the nation’s top vaccine manufacturers announced it was recalling 1.2 million doses and suspending production indefinitely.

Meanwhile, worried parents were calling doctors’ offices to ask whether their children are safe if they recently got the Hib vaccine, which protects against meningitis, pneumonia and other life-threatening and disabling bacterial diseases. Parents were told there’s virtually no chance of anything but swelling and redness around the injection, which would have happened within a week; there have been no such reports.

But health officials are still scrambling over how to address the shortage, caused by a sterility problem at a Merck & Co. vaccine factory in West Point, Pa.

“This one’s a huge challenge,” said Dr. Lance Rodewald, head of immunization services at the Centers for Disease Control and Prevention.

Rodewald said the CDC and other groups are weighing options to stretch the supply of Hib vaccine from the only other manufacturer, Sanofi Pasteur, and waiting to hear whether it can boost production or shift some doses here that normally would be sold overseas.

The American Academy of Pediatrics is advising its 60,000 members to try to order now from Sanofi Pasteur, and if they run short, to delay the booster usually given at 12-15 months.

Merck supplies about half of the 14 million doses of Hib vaccine used in the U.S. each year. It said that in addition to the doses recalled – roughly four months of production – it has quarantined nearly a year’s worth of other, possibly suspect doses and doesn’t expect to supply any more until at least October.